The present invention relates to stimulation treatments of subterranean formations primarily in the field of oil well drilling. More specifically, the present invention relates to a method and apparatus for ramping of stimulation chemical concentrations for treatment of subterranean formations primarily in the area of acidizing a borehole.
Acidizing a borehole in the field of oil well drilling is well known. This process is generally employed when petroleum exists in a formation but is unable to flow readily into the borehole because the surrounding formation has a very low permeability to the petroleum. Certain formation compositions (e.g., limestone or dolomite) dissolve in response to a chemical reaction when exposed to certain acids. The acidizing process may be done with a drill rig in place, however this is not required. The acidizing process comprises injecting an acid (e.g., hydrochloric or other acid) into the formation under pressure. The acid etches the formation, enlarging pore spaces and passages thereby providing a way for the oil or gas in the formation to enter the borehole. The acid is held under pressure for a period of time and then pumped out. The borehole is then swabbed and put back into production. It is also known to combine chemical inhibitors with the acid to prevent corrosion of the drill pipe. The acid is currently batch mixed and pumped into the borehole through a tube at a specific concentration.